Synthesis process for aromatics



United States Patent" 2,768,961 SYNTHESIS PROCESS FOR AROMATICS Herman I. Week, Hammond, and Herman S. Seelig, Valparaiso, Ind., assignors to Standard Oil Company, Chicago, 11]., a corporation of Indiana Application June 23, 1953, Serial No. 363,514

12 Claims. (Cl. 260449) This invention relates to a process for the synthesis of hydrocarbons, particularly aromatic hydrocarbons, from mixtures of carbon monoxide with hydrogen in the presence of catalysts.

In the well-known Fischer-Tropsch synthesis, iron-type or alkali-promoted thoria catalysts have been employed to produce parafiins and olefins, accompanied by very minor proportions, at most, of aromatic hydrocarbons synthesis process which can be operated to produce substantial yields of liquid hydrocarbons boiling substantially within the gasoline boiling range and comprising predominantly or entirely relatively low boiling liquid aromatic hydrocarbons of high'octane value." -Another object of this invention is to provide suitable catalysts for the production of aromatic hydrocarbons 'in substantial yields from mixtures of carbon monoxide and hydrogen. An additional object is to provide both catalysts and processing conditions whose employment in the reduction of carbon monoxide results in substantial yields of relatively low boiling aromatic hydrocarbons.

Essentially, the process of the present invention comprises the contacting of catalysts hereinafter defined with mixtures of hydrogen and carbon monoxide having molar ratios between about Mt and at temperatures between about 600 F. and about 900 F. and pressures of at least about 400 p. s. i. g. upto aboutl0,000 p. s. i. g. or I even higher, e. g. 25,000 p. s. i. g., at space velocities (volume of gasper hour per volume of catalyst) of at least about up to about 5000 (in fixed-bed reactors) .oreven much higher, for example up toabout 20,000 (in fluidizedbed reactors). The preferred temperature range is about 750 F. to about 850 F. and the preferred pressure range is about 1000 to about 6000 p. s. i. g.

The catalysts employed in the practice of the present invention comprise essentially chromia supported upon an activated alumina (gamma alumina) containing less than about 0.3 w. percent (preferably less than 0.1 w. percent) of alkali metal (calculated as alkali metal oxide) and containing an acid-acting fluoride and/ or chloride as a promoter. The proportion of acid-acting fluoride or chloride, calculated as the corresponding hydrogen halide,

"ice

in the catalyst can be varied between about 0.1 and about 1 W. percent, but it is preferably present within the catalyst in proportions between about 0.1 and about 0.4 w. percent. As will appear hereinafter, the proportion of chromia in the catalyst must be closely controlled in order to secure the best yields of aromatic hydrocarbonsin the synthesis. The proportion of chromia in the finished catalyst can be varied between about 1 and about 15 w. percent, and is preferably between about 3 and about 15 W. percent. In lieu of the alumina support or in partial replacement thereof, we may employ titania or vanadia.

Although chromia-alumina catalysts have heretofore been employed for the reduction of carbon monoxide to produce hydrocarbons, including aromatic hydrocarbons, the yields of aromatic hydrocarbons have been low for two reasons not appreciated by prior art investigators:

(1) Alumina, as ordinarily prepared by the precipitation of aluminum nitrate with sodium carbonate followed by repeated washings with water and drying, contains of the order of 1.5 w. percent of NazO. Although alkali metal oxides are desirable promoters for thoria and irontype synthesis catalysts, even very small proportions of alkali metal oxide prevent the formation of aromatic hydrocarbons when present in chromia-alumina catalysts.

a (2) Acid-acting fluorides and chlorides are remarkable promoters for chromia-alumina catalysts in that they induce a very large increase in the yield of aromatic hydrocarbons in the synthesisprocess while inducing only a relatively minor increase in the extent ofcarbon monoxide conversion. Moreover, as will be described in detail hereinafter, acid-acting fluorides and chlorides substantially aifect the distribution of individual components .in the liquid products of the synthesis reaction. As a consequence of the present invention, new sources of industrially attractive aromatic hydrocarbons become available.

The chromia-alumina catalysts having an alkali metal oxide content below about 0.3 w. percent can be prepared by known methods or combinations of known methods. A particularly desirable method of making an "activated alumina containing little or no alkali metal oxide involves the preparation of an alumina sol by the reaction of aluminum amalgam with a dilute solution of an organic acid such as formic acid or'acetic acid, which sol is then treated with ammonium hydroxide to precipitate a super-pure alumina gel containing little or no alkali metal oxide; this :is the so-called indiana alumina sol technique. References to the preparation of super-pure alumina sols arev given in our copending application Serial No. 325,778, filed December 13, 1952, now Patent No. 2,727,055.

.In order to prepare a chromia-alumina catalyst,a soluble chromium salt such as chromium. nitrate may. be added to the alumina sol before precipitation. The acidacting fiuorideor chloride may also be incorporated with the chromium nitrate and the alumina sol, in proportions desirable to effectively promote the selective synthesis ac- HF via thermal decomposition. 'rides include acetyl fluoride, propionyl fluoride, hexahyalkali metal oxide, viz. below about 0.1 w. percent.

' and carbon monoxide.

suitable temperature (for example, about 185 F.) and finally calcining the catalyst in air, for example at a temperature of about 900 F. It will be understood that the alumina component of the catalyst may be partially or completely replaced by titania or vanadia of suitably loW alkali content. Before employment of the catalysts in synthesis, they may be pretreated with hydrogen, suitable conditions being a temperature of about 900 F., hydrogen pressure of 300 p. s. i. and space velocity of 200 volumes of hydrogen per hour per volume of catalyst for about hours.

The acid-acting fluorides employed to promote chromiaalumina catalysts are HP or materials capable of forming hydrogen fluoride by thermal or hydrolytic decomposition at or below the temperatures employed in the synthesis operation. Since the chromia-alumina catalysts inevitably contain water as prepared (usually about 1 to 10 w. percent Water), they may be prepared with materials which are capable of reacting with Water to yield hydrogen fluoride; such materials include fluorine, potassium acid fluorides, ammonium acid fluorides, ClFg, BrFa, BFs, carbonyl fluoride, acyl fluorides and reactive alkyl fluorides, although the alkyl fluorides may be used as sources of Examples of acyl fluodrobenzoyl fluoride, etc. Alkyl fluorides include ethyl 1 fluoride, isopropyl fluoride, sec-butyl fluoride, cyclohexyl fluoride, etc. In lieu of or in addition to ammonium fluoride or ammonium acid fluorides, We may employ various may be achieved through treatment of the refractory metal oxide catalyst support (alumina or the like) prior to the incorporation of the chromia component; by treatment of the chromia component of the catalyst; by treatment of the chromia-alumina catalyst prior to or after drying or calcining; by the introduction of acid-acting fluoride or chloride into the reactor during synthesis, for example, by the inclusion of very small proportions of certain of the {acid-acting materials intermittently in proportions suflicient to activate the chromia-alumina catalyst and in the feed to affect the selectivity of the catalyst for the synthesis of aromatic hydrocarbons. The acid-acting fluoride or chloride is preferably introduced into the catalyst during itsmanufacture, as described above.

' In order more specifically to describe and illustrate the invention, without the intent unduly to limit the same,

examples are provided hereinafter. The chromia-alumina 7 catalysts employed in the examples were prepared by coprecipitation of chromia and alumina (derived from an Indiana sol) and activated by the addition of a suitable proportion of HF, ammonium fluoride or ammonium chloride before the precipitation of the metal oxides. These catalysts were characterized by their low content of The synthesis gas contained 50 mol percent each of hydrogen The catalyst was contained in a copper tube inserted Within a vertical stainless steel reactor. In a typical equipment 130 ml. of catalyst was employed. The synthesis gas was passed downwardly through the fixed bed of catalyst, thence in sequence 7 through three product separators operated, respectively,

. TABLE 1 U npromoted chromia-alumina catalyst Catalyst: 10% CrzOa on A1203. Run Conditions: 450 p. s. i. g., 500 Vg/Vc/Hr. using 1/1 Ha/CO synthesis gas as ice Run Period .1 A B O D E 24 24 24 24 120 700 800 900 975 975 6. 4 8. 8 12. 0 15. 6 18. 4 Percent 00 Conversion 1 9.0 13.0 20. 3 26.0 22.5 Product Yields 1 (grams/normal cubic meter of H2 and 00 consurued):

03+ 78 82 Aromatics 10 17 R I. of Liquid 0 1. 504 1.515 Percent Carbon Converted Total 100. 0 100. 0 100. 0 100. 0 100. 0

Aromatics Yield:

Percent of CO Converted... 3. 4 3. 87 3. 19 3.14 8. 4 Percent of CO Charged 0.31 0.50 0. 65 0.82 1. 89

1 Based on observed weight balance. Based on a carbon balance on an output basis.

TABLE 2 Catalyst: 10% Cr Os+0.5% NHF on A1203. Run Conditions: 450 p. s. i.' g., 500 Vg/Vc/Hr. using 1/1 Hz/CO synthesis gas as feed.

Run Period A B G D E F 120 120 120 120 120 700 750 800 850 900 975 0. 1 4. 4 8. 9 10. 8 12.4 14. 9 Percent 00 Conversion 2 5.8 11.7 13.0 13. 7 21.2 22.2 Product Yields 1 (grams/normal cubic meter of Hz+00 consumed):

03 60 81 159 81 82 32 Aromatics 57 77 64 47 17 2.3 R. I. of Liquid Oil 1. 535 1. 524 1. 518 1. 513 1. 513 1. 520

Percent Carbon Converted to: 1

Total 100. 0 100. 0 100. 0 100.0 100. 0 100.0

Aromatics Yield:

Percent of CO Converted..- 26.0 17. 9 20.3 14.7 5. 4 86 Percent of CO Charged 1. 51 2. 1 2. 64 2.01 1.14 19 1 Based on observed weight balance. Based on a 100% carbon balance on an output basis.

From Table 1 it will be noted that the maximum ultimate yield of aromatics which could be obtained from the unpromoted catalyst is only about 17 grams per normal cubic meter (n. c. m.) of synthesis gas and that the best results were obtained at 975 F.

The theoretical ultimate yield of aromatics in the syn thesis is of the order of 300 grams per normal cubic meter of synthesis gas containing 50 mol percent each of carbon monoxide and hydrogen. 7

From Table 2 it will be apparent that the promoted catalyst was far more active at lower temperatures, 975 F. being far too high, and that at lower temperatures within the range of 700-900 F., the yields of aromatic hydrocarbons ranged from 17 to 77 grams per 11. c. m. of synthesis gas.

The data of Table 3 show the promotion of chromia- I 5 TABLE 3 Hydrocarbon distribution: (Volume percent of aromatics) 10% 012034 0.6% NHAF on A1 03 Catalyst- 10% 0120; Carbon N0. A110; on A1 03 Analyses by infrared techinques of the aromatic hydrocarbon fractions described in Table 3 showed that the following aromatic hydrocarbons are present:

TABLE 4 Identification of aromatic hydrocarbons Carbon No. Hydrocarbons Benzene.

Toluene.

mand p-Xylene, traces o-xylene.

l-mcthyl-B-etbylbenzene, l-methyltethylbenzene,

1,2,4-trimethy1benzene, trace. mesitylene.

1,3-dimethyl-5-ethylbenzene, 1,4-dimethyl-2-ethylbenzene, 1,3-dimethyl-2-ethylbcnzene, durene, isodurene, 1,2,3,4-tetramcthylbenzene.

Pentamethylbenzene.

Z-methylnaphthalene,

identified aromatics.

hexamethylbenzene, other un- From Table 4 it will be noted that almost all the liquid product consists of benzene and benzene derivatives, almost all the substituent groups are methyl groups, and that practically all of the isomers are present.

The effect of increasing the reaction pressure from 450 p. s. i. g. to 900 p. s. i. g. (cf Table 2), is indicated in Tables 5 and 6. Table 5 affords direct comparisons with Table 2 but in obtaining the data of Table 6 the concen tration of ammonium fluoride promoter was reduced from 0.5 w. percent to 0.25 w. percent.

TABLE 5 Catalyst: CrzO3-l-0.5% NH F on A1203. Run Conditions: 900 p. s. i., 500 s. v., 1/1 Hz/CO.

Run Period C 1 Percent 00 conversion Product Yields 2 (grams/mom.

ofh+CO consumed):

R. I. of Liquid Oil 1. 516

Percent Carbon Converted to:

Aromatic Yield:

Percent of C O converted- Percent of C 0 charged.

1 Run at 212 space velocity. 2 Based on observed weight balance. 3 Based on a 100% carbon balance on an output basis.

- 6 resulted in a-large increase in the yield of aromatic hydrocarbons under otherwise constant operating conditions.

TABLE 6 Catalyst: 10% Cram-+0.25% NH4F on A1103. Run Conditions: 900 p. s. i., 500 s. v., 1/1 Hr/CO.

Run Period A B C D Hours 72 68 48 48 Temp., F 700 650 750 800 Percent Contract 13. 8 6. 9 13. 9 18. 4 Percent C0 conversion 24. 9 11.2 31. 3 33. 3 Product Yields 1 (grams/n.

H +CO consumed):

0 103 46 16 Aromatics 82 99 44 16 R. I. of Liquid O1 1. 522 1. 535 1. 508 1. 503 Percent Carbon converted to: 2

Aromatic Yield:

Percent of CO converted 24. 3 30.0 12.2 5. 6 Percent of CO charged 6. 1 3. 4 3. 8 1. 9

1 Based on observed weight balance. 2 Based on a 100% carbon balance on an output basis.

The data in Table 6 show that suitable conversions of carbon monoxide and desirable yields of aromatics (grams per normal cubic meter of hydrogen and carbon monoxide consumed) can be obtained at the high pressure with relatively low ammonium fluoride promoter concentration.

In the following table are presented data obtained with a charging stock having a 2:1 HzzCO volume ratio. From the data it will be noted that substantial conversions of carbon monoxide were obtained and that in general the carbon monoxide conversion was substantially greater than that obtained under comparable operating conditions with a comparable catalyst using a feed of equal volumes of hydrogen and carbon monoxide (cf. Table 2). It will also be noted from Table 7 that the refractive index of the liquid oil indicates that it is substantially completely aromatic. However, the ultimate yield of aromatic hydrocarbons appears to be somewhat greater with the 1:1 feed as compared with the 2:1 I-IzzCO feed.

TABLE 7 Catalyst: 11% ort0.+o.o% NH4F on A1203. Run Conditions: 450 p. s. i., 500 s. v., 2/1 Hz/CO.

Run Period A B C D E F Hours 120 120 120 120 120 Temp., "F 700 750 800 8 900 975 Percent Contraction 7. 4 7. 3 11.7 14. 1 19. 4 16. 6 Percent 00 conversion 3.5 20. 9 27. 6 29. 8 36.1 28. 4 Product Yields 1 (grams/n. c. m.

of Hz-i-CO consumed):

0 59 79 43 19 16 Aromatics 59 39 14 4 1 1 R. I. of Liquid 011..-- 1. 533 1. 522 1. 516 1. 512 Percent Carbon converted to:

Aromatic Yield:

Percent of CO converted. 9. 3 4. 4 1. 4 Percent of CO charged.-.- 2.0 1.9 1. 2 0.4

1 Based on observed weight balance. 2 Based on a 100% carbon balance on an output basis.

A further comparison at 450 p. s. i. of unpromoted chromia-alumina catalysts with promoted catalysts is afiorded by the following figures. From Figure 1 it will be noted that within the temperature range of 700 to 900F., promotion of the catalyst with acid-acting fluoride resulted in substantial increases in yields of aromatic hydrocarbons.

Figure 2 is a cross-plot of two isotherms from Figure 1 against which are related aromatics yield and weight constitution, show widely diflerent capacities for producpercent ammonium fluoride in the catalyst; From the ing aromatic hydrocarbons in the synthesis reaction, as data of Figure 2 it will be noted that an apparent will be evident from the data of Table 9 below: optimum ammonium fluoride concentration was about TABLE 9 0.5 w. percent, which is equivalent to about 0.25 w. Percent f HP in the catalyst Examples of other catalysts tested for the synthesis of i In Figure 3 are presented data on the extent of carbon aromatics monoxide conversion as a function of temperature for the three catalysts whose other characteristics were set Aromatic forth in Figures 1 and 2. V Catalyst Eg 3 1i In Figure 4 are presented data on the aromaticsversion cu.m. production capacity of 4.5 W. percent chromia-alumina catalysts promoted with 0.2 w. percent fluoride ion com- 2 -l %52g s a sp e ipitatod) 2; bined with different cations and a comparison is also zr oi i r A1205: 13 7 made of the unpromoted chromia-alumina catalyst con- 15 gj82+ 3 (Kz sn n t L- g taining 0.6 w. percent K20. Figure 4 indicates that an 6% blfi6::: j 2 acid-acting fluoride is required to promote the chromia- 021 some 1 a 1 alumina catalysts, since KF exerts only a relatively minor j $3 333 romoting effect (note Figure 1 wherein one of the o n 30D: 2 50 one Eatalysts contained no fluoride promoter). The data on 20 j g the effects of K20 in the catalyst are clearly discernible i gg gg g8 i8 gggg from Figure 4; over most of the temperature range, 5,+ iifi;i*"5K ',6, I 22 None K20 substantially repressed the production of aromatic ai f fi g gifigt E hydrocarbons by the catalyst. 9 SnOz+0.5% Nair on Al 0 14 None From Figure 5 it will be apparent that the extent of 25 6 3 $33; carbon monoxide conversion was greatest with HF- 99% B 0: on A1505: .1: 2 None promoted catalyst, somewhat lower with ammonium 90% Siozlm A1203 0 fluoride-promoted catalyst and least with KF-promoted l t at temperatures above b t 750F The above results represent the best yields which could In Figure 6 are presented data illustrating the effect Obtained in Operations at 500 Space Velocity, equimolal' of the chromia content of promoted chromia-alumina proportions of hydrogen and Carbon monqXide in catalysts on the aromatics productivity of these catalysts. feed, a fixfid bed of Catalyst, 450 P- reaction Pressure, From the data in Figure 6 it appears that a chromia and tempfifaiureiwithin tha range of to content of about 10 w. percent is optimum and that severe A11 Q alumlni'ls In Table 9 contained 1658 than losses in the ultimate yields of aromatic hydrocarbons 35 alkah metal oxldeare incurred by going to catalysts Containing 0% It Will be understood that conventional methods of chromia. synthesis catalyst regeneration can be employed to re- In Table 8 are presented data obtained with NH4Clactlvat? P Y Spent chloridefluofide-pfomPted promoted chromia-alumina catalyst. The data of Table chromla'alummd catalysts, tfeatment 0f P y 8 may be compared with those of Table 2 wherein am- 40 SPent catalyst Y g g fl to burn monium fluoride Was employed as the promoter under carbonaceous deposits. Llkewise, conventional synthesis otherwise constant operating conditions and catalyst comreactors of elfher 0T fiuldlzed-b'id WP? may position. It will be noted from Table 8 that ammonium f emPloyefi in Practlclngthe PYOCESS 0f the Pffisent Invenchloride was a Very desirable pmmmer, although thfi tlon. It will be understood that unconverted gases may chloride was somewhat less effective than the fluoride. be rscyqledto the reactor or Passedto a secondary reactor The most successful operating periods of Table 8 were 0 Contamlng the Promoted Catalyst A B and C, covgring the range of to F The aromatic hydrocarbon products of the present inventlon are practically uncontaminated with paraffins or TABLE 8 olefins. The fractions may be employed alone or as Catalyst: 10% 0r202+0.5% NH4O1 on A120 blending components in motor gasoline or aviation fuels. -C t 450 p- 00 K The aromatic product mixtures produced by the process of this invention can be subjected to known separation Run Period A B 9 D E F procedures to produce concentrates of individual aromatic hydrocarbons or mixtures of isomers, which may be of 72 72 72 72 72 72 value for the purpose of producing chemical derivatives. 1 1ito rr1t;a&ti65 I iii E 3 39 139g 1393 12. 2 Having thus described our invention, We claim: gsgg g ff gg g 1. A process for the preparation of hydrocarbons, inof HH-Go consumodf cludlng a substantial proportion of aromatic hydrocar- 4 bons, Which process comprises contacting a mixture of hydrogen and carbon monoxide in a volume ratio between about 1:4 to 4:1 with a catalyst comprising essentially about 1 to about 15 weight percent chromium oxide supported upon a gamma alumina, between about 0.1 and about 1 weight percent of an acid-acting halide selected Aromatic Yield from the group consisting of fluorides and chlorides, calu- Percemofc'o couvertednn 15.3 19 Q6 lated as the hydrogen halide, and not more than about Percent OfGO charged 0.3 weight percent of alkali metal, calculated as oxide, eiiecting said contacting at a temperature between about 333 8 gblsotagedaugeirglhg llJalance. n t ut bapis 600 F. and about 900 F. at a pressure of at least about c r 0 a wee on a on p 400 p. s. i. g., and separating synthesis products including The proper selection and activation of catalysts for the a substantial proportion of aromatic hydrocarbons.

purpose of aromatics production from carbon monoxide 2. The process of claim 1 wherein the volume ratio of and hydrogen is at present a purely empirical procedure, hydrogen to carbon monoxide is about 1. since no method of predicting the suitability of catalysts 3. The process of claim 1 wherein the temperature is or promoters for the stated purpose is now known. Apbetween about 600. 'F. and about 850 F.

parently similar catalysts, from the standpoint of chemical 4. A process for the preparation of hydrocarbons, in-

cluding a substantial proportion of aromatic hydrocarbons, which process comprises contacting a mixture of hydrogen and carbon monoxide in a volume ratio between about 1:4 to 4:1 with a catalyst comprising essentially about 1 to about 15 weight percent chromium oxide supported upon a gamma alumina, between about 0.1 and about 1 weight percent of an acid-acting fluoride, calculated as HF, and not more than about 0.3 weight percent of alkali metal, calculated as oxide, effecting said contacting at a temperature between about 600 F. and about 900 F. at a pressure of at least about 400 p. s. i. g., and separating synthesis products including a substantial proportion of aromatic hydrocarbons.

5. A process for the preparation of hydrocarbons, including a substantial proportion of aromatic hydrocarbons, which process comprises contacting a mixture of hydrogen and carbon monoxide in a volume ratio between about 1:4 to 4:1 with a catalyst comprising essentially about 1 to about 15 Weight percent chromium oxide supported upon a gamma alumina, between about 0.1 and about 1 weight percent of an acid-acting chloride, calculated as HCl, and not more than about 0.3 weight percent of alkali metal, calculated as oxide, effecting said contacting at a temperature between about 600 F. and about 900 F. at a pressure of at least about 400 p. s. i. g., and separating synthesis products including a substantial proportion of aromatic hydrocarbons.

6. A process for the preparation of hydrocarbons, including a substantial proportion of aromatic hydrocarbons, which process comprises contacting a mixture of hydrogen and carbon monoxide in a volume ratio between about 124 to 4:1 with a catalyst consisting essentially of about weight percent chromia supported upon activated alumina, said catalyst containing between about 0.1 and about 0.4 weight percent of an acid-acting fluoride, calculated as HF, said catalyst containing not more than about 0.1 weight percent of an alkali metal, calculated as oxide, said contacting being eflected at a temperature between about 600 F. and about 850 F. at a pressure of at least about 400 p. s. i. g.

7. The process of claim 6 wherein said acid-acting fluoride is hydrogen fluoride.

8. The process of claim 6 wherein said acid-acting fluoride is ammonium fluoride.

9. A process for the preparation of hydrocarbons, including a substantial proportion of aromatic hydrocarbons, which process comprises contacting a mixture of hydrogen and carbon monoxide in a volume ratio between about 1:4 to 4:1 with a catalyst consisting essentially of about 10 weight percent chromia supported upon activated alumina, said catalyst containing between about 0.1 and about 0.4 weight percent of an acid-acting chloride, calculated as HCl, said catalyst containing not more than about 0.1 weight percent of an alkali metal, calculated as oxide, said contacting being eflected at a temperature between about 600 F. and about 850 F. at a pressure of at least about 400 p. s. i. g.

'10. The process of claim 9 wherein said acid-acting chloride is hydrogen chloride.

11. The process of claim 9 wherein said acid-acting chloride is ammonium chloride.

12. A process for the preparation of hydrocarbons, including a substantial proportion of aromatic hydrocarbons, which process comprises contacting a mixture of hydrogen and carbon monoxide in a volume ratio between about 1:4 to 4:1 with a catalyst comprising essentially about 1 to about 15 weight percent chromium oxide supported upon a gamma alumina, between about 0.1 and about 1 weight percent of an acid-acting halide selected from the group consisting of fluorides and chlorides, calculated as the hydrogen halide, and not more than about 0.1 weight percent of alkali metal, caluculated as oxide, effecting said contacting at a temperature between about 600 F. and about 900 F. at a. pressure of at least about 400 p. s. i. g., and separating synthesis products including a substantial proportion of aromatic hydrocarbons.

References Cited in the file of this patent UNITED STATES PATENTS 2,194,186 Pier et al Mar. 19, 1940 2,422,372 Smith et a] June 17, 1947 2,500,146 Fleck et al Mar. 14, 1950 OTHER REFERENCES Haensel: Office of Technical Services Report No. PB 284, pp. 6 to 9 (Jan. 11, 1946), Dept. of Commerce, Washington, D. C.

Storch et al.: The Fischer-Tropsch and Related Synthesis, John Wiley & Sons, Inc., New York (1951), pages 7, 225 and 458. 

1. A PROCESS FOR THE PREPARATION OF HYDROCARBONS, INCLUDING A SUBSTANTIAL PROPORTION OF AROMATIC HYDROCARBONS, WHICH PROCESS COMPRISES CONTACTING A MIXTURE OF HYDROGEN AND CARBON MONOXIDE IN A VOLUME RATIO BETWEEN ABOUT 1:4 TO 4:1 WITH A CATALYST COMPRISING ESSENTIALLY ABOUT 1 TO ABOUT 15 WEIGHT PERCENT CHROMIUM OXIDE SUPPORTED UPON A GAMMA ALUMINA, BETWEEN ABOUT 0.1 AND ABOUT 1 WEIGHT PERCENT OF AN ACID-ACTING HALIDE SELECTED FROM THE GROUP CONSISTING OF FLUORIDES AND CHLORIDES, CALULATED AS THE HYDROGEN HALIDE, AND NOT MORE THAN ABOUT 0.3 WEIGHT PERCENT ALKALI METAL CALCULATED AS OXIDE, EFFECTING SAID CONTACTING AT A TEMPERATURE BETWEEN ABOUT 600* F. AND ABOUT 900* F. AT A PRESSURE OF AT LEAST ABOUT 400 P. S. I. G., AND SEPARATING SYNTHESIS PRODUCTS INCLUDING A SUBSTANTIAL PROPORTION OF AROMATIC HYDROCARBONS. 